The present invention relates generally to glass supporting and conveying apparatus and, more particularly, to a finely adjustable shifting arrangement for specially configurated, flexible, pivotal conveyor rolls utilized in a press bending apparatus.
In one known commercial production of curved or bent glass sheets in large quantities, such as is encountered in the mass production of glazing closures for automobiles and the like, the sheets are supported in a horizontal plane and advanced in a horizontal path on externally driven roll-type conveyors successively through a heating area, a bending area and a heat treating area for annealing or tempering the bent sheets. The heated glass sheets are advanced from the heating furnace into the bending area and accurately located therein between complemental upper and lower shaping members by the engagement of the leading edges thereof with locating stops positioned in the path of movement of the advancing sheets. When properly oriented, the sheet is engaged along its marginal edge portions by the lower press member and lifted from the conveyor rolls for pressing between the complemental shaping surfaces of the press members to the desired curvature.
One problem encountered in the production of glazing closures by the above described process is the occurrence of certain optical defects, commonly known as "roll distortion", in the finished glazing closures. Such distortion is caused by the marring of the glass sheet surfaces due to the relative frictional movement between the glass surfaces and the rotating conveyor rolls when the sheet is in the heat-softened condition necessary for proper bending. This relative movement is most likely to occur advancing movement of the sheet is interrupted by the locating stops while the conveyor rolls continue to rotate. Even if the timing is precisely controlled so that the initiation of the glass lifting operation occurs simultaneously upon glass stoppage to avoid any time lag therebetween, the heat-softened central portions of the glass sheets located inwardly of the press contacting marginal edges thereof sag sufficiently to remain in contact with the rotating conveyor rolls for at least a limited time. While this distortion can be tolerated in vertically disposed glazing closures, it becomes more pronounced in those glazing closures intended for mounting at relatively sharp angles, such as the backlights of the more recently styled automobiles for example, and poses serious optical problems interferring with clear or true vision therethrough.
The method and apparatus disclosed and claimed in U.S. Pat. No. 3,905,794, granted Sept. 16, 1975, and assigned to the same assignee as the present invention, provided a solution to the problem of objectionable roll distortion by utilizing a series of conveyor rolls having arcuately curved central portions normally disposed in an upper common horizontal plane for supporting a flat sheet of heat-softened glass to be bent and pivotable into a lower position out of engagement with said flat sheet upon engagement thereof along its marginal edge portions by the shaping rail of an upwardly movable female press member. The present invention constitutes an improvement over U.S. Pat. No. 3,905,794 by making certain improvements in the actuator for pivoting the rolls in unison and for precisely adjusting and the maintaining the conveyor rolls in their desired angular attitudes.